[sdiy] Tube amp cap discharge tool?

[Roy J. Tellason]

On Wednesday 18 May 2005 02:14 pm, WeAreAs1 at aol.com wrote:
> Hello DIY dudes,
>
> Can anyone give me a quick recipe for a safe tube amp capacitor discharging
> tool?  That is, something I can use to discharge the voltages found on
> filter caps in tube amps after you turn the amp off, so it will be safe to
> stick my hands and tools in there to work on them.  I'm guessing that I
> need something like a fairly large value, high wattage resistor connected
> on one end to a test clip that I hook onto chassis ground, using the other
> end of the resistor to touch the hot side of the charged-up capacitors to
> shunt the charge to ground, but I'd like to know for sure if this is the
> right way to do it, and if so, what value should I use for the resistor
> (both resistance and wattage).  Any other tips about precautions,
> procedure, or techniques would be much appreciated. Sorry to be such a
> pussy about this, but for some odd reason, I am not so much in the mood for
> electrocuting myself today.

I'd say that the required value will depend much on the voltages that the 
supply normally sees,  the values of the capacitors,  and the normal current 
levels.

What *I* would do is add bleeder resistors in there,  across the caps.  You 
probably can't go too far wrong with something like 100k ohms,  though you 
may have to wait a while for complete discharge.  For a lot of stuff 10k ohms 
is going to be too low a value.  So what you want is somewhere in between.

Let me know,  offlist if you want,  and we'll figure it out -- I also have a 
fair amount of 2W and bigger resistors kicking around,  since I started 
working on this stuff when it was all tubes...